Just did the test with the drop-down menu on Chromium 71.0.3578.80 and Firefox 63.0.3 both running on Ubuntu 18.10. I can confirm the difference in performance,

Just did the test with the drop-down menu on Chromium 71.0.3578.80 and Firefox 63.0.3 both running on Ubuntu 18.10. I can confirm the difference in performance, FF takes at least 1s longer to open the menu